nfs: always update creds in mirror, even when we have an already connected ds
nfs: always update creds in mirror, even when we have an already connected ds

A ds can be associated with more than one mirror, but we currently skip
setting a mirror's credentials if we find that it's already set up with
a connected client.

The upshot is that we can end up sending DS writes with MDS credentials
instead of properly setting them up. Fix nfs4_ff_layout_prepare_ds to
always verify that the mirror's credentials are set up, even when we
have a DS that's already connected.

Reported-by: Tom Haynes <aa207f46ec5f0366c32caebc1d62b16759619d8d@primarydata.com>
Signed-off-by: Jeff Layton <542dfe392278ff3cf017aafde9d989e8068d5c3e@primarydata.com>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org # 4.0+
Signed-off-by: Trond Myklebust <cc958843532c615cbd4920e868f78c7985331a5a@primarydata.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs